DE112007000094B4 - Vehicle steering control apparatus - Google Patents

Abstract

A vehicle steering control device (30) comprising: a steering force applying device (10, 15) for applying a steering force to at least front wheels (5, 6); and characterized by a lateral guide force detecting device (42) for detecting a cornering force (Ff, Fr) of both the front wheels (5, 6) and the rear wheels (7, 8), the steering force applying device (10, 15) acting on the front wheels (5, 6 ) applies a first steering force which steers the front wheels (5, 6) in a direction to which a yaw vibration converges if a ratio of the cornering force (Fr) of the rear wheels (7, 8) to the cornering force (Ff) of the front wheels (5 , 6) becomes a ratio possibly causing the yaw vibration in the vehicle (1).

Description

Technical area

The present invention relates to a vehicle steering control device according to the preamble of claim 1.

State of the art

A vehicle such as a motor vehicle employs an electric power steering apparatus that applies a steering assist torque to a steering mechanism including front wheels by driving an electric motor in accordance with a steering torque applied by a driver (or a crew) by operating a steering wheel. In such an electric power steering device, as disclosed in Japanese Published Patent Application JP 2004-203112 A or the basis for the preamble of claim 1 forming EP 1 433 689 A2 is disclosed in the same patent family, a phase compensation (ie, a damping control) with respect to a target value of a base auxiliary current is performed, which is supplied to the electric motor in accordance with the applied steering assist torque. Due to this structure, a damping component can be taken into account, which enables an improvement in the convergence behavior of the steering.

The JP 2003-267244 A teaches to determine the risk of yaw vibrations based on the steering frequency and, if appropriate, to initiate a corresponding compensation torque to reduce or prevent detected yaw oscillations.

The WO 02/074 638 A1 discloses applying a compensating torque to the steering system for vehicle stabilization, wherein detected yaw oscillations serve as a control variable.

Disclosure of the invention

Problem to be solved by the invention

In order to improve the convergence behavior of the steering of the vehicle as described above, ie to achieve a decrease in the vibrations of the steering, one possible measure is to increase the aforementioned damping control. However, if the damping control is increased, the steering wheel steering feeling of the driver becomes poor. More specifically, the increase in the damping control gives a viscous or heavy impression when operating the steering wheel and gives an impression such that the direction of travel of the vehicle does not correspond to the driver's desire. On the other hand, if the damping control is reduced, a steering vibration and a yaw vibration, ie, an alternately increasing and decreasing yaw rate, are coupled to each other depending on the vehicle characteristic (or structure or the like), which may deteriorate the convergence behavior of the entire vehicle. That is, the phase of the steering vibration and the phase of the yaw vibration of the vehicle are in a reverse phase relationship, possibly increasing the vibration applied to the entire vehicle.

In view of the above problem, therefore, an object of the present invention is to provide a vehicle steering control apparatus which can improve the convergence behavior of a vehicle while improving the convergence behavior of a steering, in other words, the yaw rate becomes faster to a constant yaw rate so that the steering vibration decreases.

This object is achieved by a vehicle steering control device having the features of claim 1. Advantageous developments are the subject of the dependent claims.

Incidentally, the "front wheels" of the present invention indicate wheels relatively arranged on the front side with respect to the traveling direction of the vehicle, and the "rear wheels" of the present invention indicate wheels relatively in relation to the running direction of the vehicle rear side are arranged.

If the ratio of the cornering force of the rear wheels to the cornering force of the front wheels in a device according to claim 2 becomes the ratio which possibly causes a yaw vibration in the vehicle, according to this aspect, the front wheels may be in accordance with the steering direction by a driver (ie, in accordance with, whether the steering wheel is turned or retracted) toward the neutral position or the end direction in comparison with the case where there is no possibility that the cornering force generated on the rear wheels causes the front wheels to vibrate, or in case there is no possibility that the yaw vibration occurs in the vehicle. This can prevent the steering vibration and the yaw vibration from being coupled with each other even if there is a possibility that the cornering force of the rear wheels vibrates the front wheels or even if there is a possibility that a yaw vibration is occurring in the vehicle. This can cause the convergence of the vibration of the front wheels. That is, it is possible to understand the convergence behavior of the vehicle under Improving the convergence behavior of the steering.

According to an apparatus according to claim 3, the above-mentioned effect can be obtained in a so-called active steering mechanism (i.e., a steering mechanism for performing steering control by inputting a turning angle).

According to in an apparatus according to claim 4, as compared with the case where the turning angle can be directly controlled, it is possible to obtain the above-mentioned advantage to improve steering feeling.

According to an apparatus according to claim 5, it can be judged that there is a possibility that a yaw vibration will occur in the vehicle if the ratio of the cornering force of the rear wheels to the cornering force of the front wheels is greater than the first predetermined threshold.

Incidentally, a yaw vibration in the vehicle often occurs mainly after cornering of the vehicle. Thus, the judgment as to whether or not the possibility that a yaw vibration occurs in the vehicle may be made when cornering the vehicle.

Since the cornering force of the front wheels can be estimated from the turning angle of the front wheels, it can be judged that there is a possibility that the yaw vibration occurs in the vehicle if the ratio of the cornering force of the rear wheels to the turning angle of the rear wheels is estimated Front wheels is greater than the second predetermined threshold.

In the vehicle having a comparatively high vehicle height such as a minivan and SUV (Sport Utility Vehicle), the generation of cornering force of the front wheels or the rear wheels due to ringing or reactive swing in the roll direction is delayed. Therefore, in a device according to claim 7, even in the vehicle having the comparatively high vehicle height, it is possible to desirably judge whether or not there is a possibility that a yaw vibration is occurring in the vehicle.

According to an apparatus according to claim 8, it is possible to compute the convergence steering force in a desirable manner. Incidentally, the sum of the proportional value of the cornering force of the rear wheels and the differential value of the cornering force of the rear wheels may be calculated as the convergence steering force.

According to a device according to claim 9, the vehicle behavior can be stabilized even if the speed of the vehicle changes. In particular, the convergence steering force can be reduced with increasing speed of the vehicle.

Incidentally, at least one of the proportional value of the cornering force of the rear wheels and the differential value of the cornering force of the rear wheels, which is a basis in the calculation of the convergence steering force, may be corrected in accordance with the speed of the vehicle. In this case, a coefficient (in other words, a gain factor) for at least one of the proportional value of the cornering force of the rear wheels and the differential value of the cornering force of the rear wheels may be corrected in accordance with the speed of the vehicle when the convergence steering force is calculated. In addition, with increasing speed of the vehicle, the coefficient can be further reduced. Further, a sign of the proportional value of cornering force at a certain speed of the vehicle in a neutral steering state may be reversed.

By constructing a device according to claim 10, even if the speed of the vehicle changes significantly on a rough road (particularly, for example, an uneven road, a low μ road, or the like), the convergence steering force can be applied in order to realize a comparatively desirable steering.

By constructing a device according to claim 11, it is possible to calculate the convergence steering force by reducing the contribution ratio of the differential value of the cornering force, which increases the susceptibility to failure due to the rough road driving. Therefore, an excessive or significantly changing convergence steering force can be prevented from being applied.

Incidentally, the convergence steering force may be calculated based on the proportional value of the cornering force by setting the contribution ratio of the differential value of the cornering force to zero.

According to an apparatus according to claim 12, it is possible to calculate the convergence steering force very accurately on the basis of the momentum of the vehicle generated by the vehicle. D. that is, instead of calculating the steering force only from an allocation table or the like, the steering force may theoretically be calculated based on an actual movement model of the vehicle. Thus, the convergence steering force can be calculated very accurately.

By constructing a device according to claim 13, it is possible to calculate the convergence steering force very accurately on the basis of the pulse generated by the vehicle and the moment when the front wheels are steered.

According to an apparatus according to claim 14, considering that the driver is a change in the steering feeling (eg, a change in a steering torque) in the range that the absolute value of the steering angle and / or the absolute value of the steering speed are comparatively small Feeling light, by reducing the convergence steering force (moreover, by reducing the convergence steering force to the limit, thereby setting the convergence steering force to 0), it is possible to prevent the steering feeling from deteriorating.

Incidentally, instead of applying the convergence steering force (that is, setting the convergence steering force to 0), a base steering force which is a steering force based on the steering torque according to the driver's steering operation may be applied. Similarly, in the explanation below, when the convergence steering force is reduced, the base steering force may be set to 0 by setting the convergence steering force.

According to an apparatus according to claim 15, taking into account that there is a high possibility that the driver is conducting a steer to steer clear of an obstacle if the absolute value of the steering angle and the absolute value of the steering speed are excessively large, deteriorating by reducing the convergence steering force the evasive maneuver can be prevented.

According to an apparatus according to claim 16, taking into consideration that there is a high possibility that the driver will steer the steering operation to avoid an obstacle, if the steering direction is opposite to the direction in which the steering force is applied, the deterioration avoidance maneuver can be prevented in that the convergence steering force is reduced or the convergence steering force is set to 0.

According to an apparatus according to claim 17, the driver's steering feeling can be prevented from being degraded by steering the rear wheels. In this case, the base steering force can be applied to the front wheels.

By constructing a device according to claim 18, when a steering vibration is occurring or is about to occur, the stability of the vehicle beyond the avoidance maneuver can be improved (i.e., the occurrence of yaw vibration can be prevented) by applying the convergence steering force.

According to an apparatus according to claim 19, the convergence steering force is reduced considering that the cornering force of the rear wheels is easily changed or a predetermined cornering force is not necessarily obtained by steering the front wheels when a longitudinal force control (particularly, for example, an ABS (Antilock Brake System)). Control, a VSC (vehicle stability control), a TRC (traction control)) is performed.

In addition, in addition to the case where the longitudinal force control is being performed, the convergence steering force can be reduced even when there is a high possibility that the longitudinal force control is started.

By constructing a device according to claim 20, it is possible to increase the convergence steering force by reducing the contribution ratio of the lateral force proportional value which can change significantly due to the longitudinal force control (in other words, by increasing the contribution ratio of the differential value of the cornering force due to the change in the speed of the vehicle does not change so significantly). Therefore, an excessive or significantly changing convergence steering force can be prevented from being applied.

Incidentally, the convergence steering force may be calculated on the basis of the differential value of the cornering force by setting the contribution ratio of the proportional value of the cornering force to zero. Similarly, in the explanation below, when the contribution ratio of the lateral force is reduced in proportion, the convergence steering force can be calculated based on the differential value of the cornering force by setting the contribution ratio of the proportional value of the cornering force to zero.

By a construction of a device according to claim 21, if the proportional value of the cornering force can change significantly even after completion of the longitudinal force control, then First, the convergence steering force can be calculated on the basis of the differential value of the cornering force, and then the convergence steering force based on the proportional value and the differential value by increasing the contribution ratio of the proportional value in accordance with the change in the proportional value in the cornering force in FIG Course of time gradually decreases, be calculated.

According to an apparatus according to claim 22, it is possible to increase the convergence steering force by reducing the contribution ratio of the proportional value of the cornering force, which can change significantly due to the high acceleration or deceleration (in other words, by increasing the contribution ratio of the differential value of the cornering force which is due to the change in the speed of the vehicle does not change so significantly). Therefore, an excessive or significantly changing convergence steering force can be prevented from being applied.

Incidentally, during the occurrence of pitching due to the high acceleration or deceleration, the convergence steering force may be reduced, as compared with the case where no pitch occurs, based on both the proportional value of cornering force of the rear wheels and the differential value of cornering force of the rear wheels Contribution ratio of the proportional value of the cornering force of the rear wheels are calculated.

The proportional value of the cornering force may change significantly in the predetermined period after the acceleration or deceleration begins to change (in other words, in the period until a pitching vibration of the vehicle caused by the acceleration or deceleration converges) , Therefore, according to an apparatus of claim 23, the convergence steering force can be calculated by reducing the contribution ratio of the proportional value. Therefore, an excessive or significantly changing convergence steering force can be prevented from being applied. That is, during the occurrence of pitching due to high acceleration or deceleration, the convergence steering force can be compared with the case where no pitch occurs based on both the proportional value of the cornering force of the rear wheels and the differential value of the cornering force of the rear wheels by reducing the contribution ratio of the proportional value of the cornering force of the rear wheels.

According to an apparatus according to claim 24, the convergence steering force is considered in consideration that the cornering force of the rear wheels slightly changes or the desired cornering force is not necessarily achieved by steering the front wheels, if a load control (in particular, for example, a suspension control, stabilizer control or the like) is performed, reduced.

Moreover, in addition to the case that the load control is actually performed, the convergence steering force can be reduced even in the case that there is a high possibility that the load control is started. The convergence steering force can be further reduced as a change per unit load increases. In addition, as in the case that the longitudinal force control is performed, the convergence steering force based on the proportional value of the cornering force of the rear wheels and the differential value of the cornering force of the rear wheels to reduce the contribution ratio of the proportional value of the cornering force of the rear wheels compared to the case that the load control is not performed, be calculated.

According to an apparatus according to claim 25, the convergence steering force is reduced in consideration of the fact that the cornering force of the rear wheels slightly changes due to the screwing in, or the desired cornering force is not necessarily obtained by the steering of the front wheels.

Incidentally, if there is a possibility that screwing-in occurs or if screwing-in actually occurs, the steering force that can steer the front wheels in a direction to avoid skidding of the vehicle may be applied to ensure the stability of the vehicle.

According to a device according to claim 26, even if there is a possibility that the cornering force generated on the rear wheels, the front wheels are vibrated, or if there is a possibility that a yaw vibration occurs in the vehicle, be prevented Steering vibration and the yaw vibration are coupled together by the natural frequency value of the front wheels is changed. This can lead to a convergence in the vibration of the front wheels. That is, it is possible to improve the convergence behavior of the vehicle while improving the convergence behavior of the steering.

By a structure according to claim 26, the cornering ability is changed by steering the front wheels in the towing direction. Therefore, it is possible to change the natural frequency value of the front wheels.

These effects and other advantages of the present invention will become more apparent from the embodiment explained below.

Brief description of the drawings

1 Fig. 10 is an outline structural view conceptually showing the basic construction of an embodiment of the vehicle steering control apparatus of the present invention.

2 FIG. 11 is a flowchart conceptually showing an entire operation of an electric power steering apparatus. FIG.

3 FIG. 15 is a flowchart showing a procedure of calculating a target steering torque in step S200 in FIG 2 shows.

4 FIG. 15 is a flowchart conceptually showing the procedure of judgment of an over-state in step S210 in FIG 3 shows.

5 FIG. 14 is a flowchart conceptually showing the procedure of a judgment of a reverse assist in step S220 in FIG 3 shows.

6 Fig. 10 is a diagram showing a steering angle and a steering speed.

7 FIG. 14 is a flowchart conceptually showing the procedure of calculating a basic steering torque in step S230 in FIG 3 shows.

8th FIG. 12 is a diagram showing a relationship between a steering torque and the base steering torque. FIG.

9 FIG. 14 is a flowchart conceptually illustrating the procedure of calculating a convergence steering torque in step S240 in FIG 3 shows.

10 FIG. 12 is a diagram showing a relationship between a vehicle speed dependency coefficient and a vehicle speed. FIG.

11 FIG. 12 is a diagram showing a relationship between a vehicle speed dependency coefficient and a vehicle speed. FIG.

12 Fig. 15 is a graph showing the value of a longitudinal acceleration coefficient with respect to the absolute value of the longitudinal acceleration.

13 FIG. 15 is a graph showing the value of the longitudinal acceleration coefficient with respect to an elapsed time from the beginning of a change in the longitudinal acceleration.

14 Figure 13 is a graph showing the values of ABS coefficients with respect to time.

15 Fig. 10 is an outline structural view conceptually showing the basic structure of a first modified example of the embodiment of the vehicle steering control apparatus of the present invention.

16 Fig. 10 is an outline structural view conceptually showing the basic structure of a second modified example of the embodiment of the vehicle steering control apparatus of the present invention.

LIST OF REFERENCE NUMBERS

1

vehicle

5, 6

front

7, 8

rear wheel

10

electric power steering device

11

steering wheel

13

Steering angle sensor

14

torque sensor

15, 55

electric motor

30

ECU

31

Wankwinkelberechnungsschaltung

32

Eindrehbeurteilungsschaltung

33

ABS control circuit

34

SUS (wheel suspension) control circuit

41

Vehicle speed sensor

42

Cornering force sensor

61, 62

active steering wheel

Best way to carry out the invention

Hereinafter, the best mode for carrying out the invention in each embodiment will be explained in the order with reference to the drawings.

(1) basic structure

First, referring to 1 an explanation will be given on the basic construction of an embodiment of the vehicle steering control apparatus of the present invention. 1 FIG. 10 is an outline construction view showing the basic structure of the embodiment of FIG A vehicle steering control apparatus of the present invention is shown in conceptual form.

As shown in 1 is a vehicle 1 with front wheels 5 and 6 and rear wheels 7 and 8th Mistake. The front wheels and / or the rear wheels are driven by a driving force obtained from a motor. At the same time, the front wheels are steered, so that the vehicle 1 can move in a desired direction.

The front wheels 5 and 6 , which are the steered wheels, are powered by an electric power steering device 10 steered in accordance with the steering action of a steering wheel 11 is driven by a driver. The electric power steering device 10 More specifically, for example, it is a rack-and-pinion electric power steering apparatus, and is provided with: a steering shaft 12 whose one end with the steering wheel 11 connected is; a rack (and pinion) mechanism 16 , with the other end of the steering shaft 12 connected is; a steering angle sensor 13 for detecting a steering angle θ, which is a rotation angle of the steering wheel 11 is; a moment sensor 14 for detecting a steering torque MT, which by steering the steering wheel 11 on the steering shaft 12 is applied; and an electric motor 15 for generating an auxiliary steering force which reduces the load of the driver when steering, and for applying the auxiliary steering force to the steering shaft 12 by means of a reduction gear, not shown.

In the electric power steering device 10 calculates an ECU 30 a target steering torque T, which is a torque transmitted by the electric motor 15 is to be generated on the basis of the steering angle θ, which from the steering angle sensor 13 is output, the steering torque MT, which from the torque sensor 14 is output, a roll angle RA of the vehicle 1 which consists of a roll angle calculation unit 31 is output, a control signal S1, which from an oversteer judgment unit 32 is output and which indicates whether an override occurs or not, a control signal 52 which consists of an ABS control circuit 33 is output and which indicates whether an ABS control is executed or not, a control signal 53 consisting of a suspension (SUS) control circuit 34 which indicates whether or not a stabilizer control or suspension control is performed, or a vehicle speed V, which is a vehicle speed sensor 41 is output, and a cornering force F _{f of} the front wheels and a cornering force spring rear wheels, which consists of a cornering force sensor 42 be issued.

In this case, the roll angle calculation unit calculates 31 the roll angle RA based on a lateral acceleration (G) generated by a side G sensor 43 is calculated. The override assessment unit 32 generates the control signal S1 indicating whether the oversteer occurs or not based on a yaw rate γ generated by a yaw rate sensor 44 is calculated, and a throttle opening amount O by a throttle opening amount sensor 45 is detected.

The target steering torque T is from the ECU 30 to the electric motor 15 output, and an electric current according to the target steering torque T is the electric motor 15 supplied by which the electric motor 15 is operated. As a result, a steering assist force from the electric motor 15 out on the steering shaft 12 applied, which leads to a reduction of the burden on the driver while steering. In addition, due to the rack and pinion mechanism 16 a force in the direction of rotation of the steering shaft 12 in a force in a back and forth direction of a rack 17 transformed. The two ends of the rack 17 are each about a tie rod or connecting rod 18 with the front wheels 5 and 6 connected, and the direction of the front wheels 5 and 6 will be in accordance with the back and forth movement of the rack 17 changed.

Incidentally, the side guide force sensor 42 the cornering forces F _f and F _r directly detect. Alternatively, instead of providing the cornering force sensor, the ECU may 42 z. B. determine the cornering forces F _f and F _r on the basis of another parameter by operation or calculation or the like. Similarly, in various other sensors, the detection target of the sensors can be detected directly by providing the sensors. Alternatively, instead of providing the sensors, the ECU 30 the detection target of the sensors z. B. on the basis of another parameter by operation or calculation or the like.

(2) Principle operation

Next, referring to 2 to 14 a more detailed explanation of the operation of the electric power steering apparatus 10 in the embodiment.

2 FIG. 10 is a flowchart showing an overall operation of the electric power steering apparatus. FIG 10 in conceptual form shows. As shown in 2 becomes the electric power steering device 10 if an ignition is ON (step S100: Yes). In particular, the target steering torque T is determined by the operation of the ECU 30 calculated (step S200), and a Steering torque control is by driving the electric motor 15 in accordance with the calculated target steering torque T (step S300).

3 FIG. 14 is a flowchart showing the procedure of calculating the target steering torque T in step S200 in FIG 2 shows. As shown in 3 Then, if the target steering torque T is calculated, it is first judged whether or not the steering is in an overshoot condition (or the possibility that the steering is in an overshoot condition) (step S210). In other words, it is judged whether the steering vibration and the yaw vibration of the vehicle are coupled with each other or not and the vehicle 1 in a shaky state (or there is a possibility of the vehicle 1 into a wobbly state). Incidentally, the flow of judgment of an overshoot condition in step S210 will be described later with reference to FIG 4 be executed.

If it is judged that the steering is not in an overshoot condition (or there is no possibility that the steering is in an overshoot condition) (step S210: No), as a result of the judgment in step S210, a basic steering torque becomes the target steering torque T calculated as referring to 7 and 8th will be executed (step S230).

On the other hand, if, as a result of the judgment in step S210, it is judged that the steering is in an overshoot condition (or there is a possibility that the steering is in an overshoot condition) (step S210: Yes), a reverse assist judgment is performed, which judges whether the steering direction of the steering wheel 11 by the driver to a direction of steering force, which is on the front wheels 5 and 6 is applied, is opposite or not (ie, whether it is a reverse support or not) (step S220). Incidentally, the process of the reverse support judgment in step S220 will be described later with reference to FIG 5 and 6 be executed.

If it is judged that the reverse assistance is present as a result of the judgment in step S220 (step S220: Yes), the basic steering torque is calculated as the target steering torque T (step S230).

If, as a result of the judgment in step S220, it is judged that the reverse assistance is not present (step S220: No), a convergence steering torque is calculated as the target steering torque T so as described with reference to FIG 9 to 14 will be executed (step S240).

4 FIG. 15 is a flow chart showing the procedure of judgment of an over-state in step S210 in FIG 3 in conceptual form shows. As in 4 In order to judge whether the steering is in an overshooting condition or not, it is first judged whether a ratio of the cornering force F _{r of} the rear wheels is judged 7 and 8th to a steering angle δ of the front wheels 5 and 6 is greater than a predetermined threshold OS1 or not (step S211).

If judged as the result of the judgment in step S211 that the ratio of the cornering force F _{r of} the rear wheels 7 and 8th to the steering angle δ of the front wheels 5 and 6 is greater than the predetermined threshold OS1 (step S211: Yes), it is judged that the steering is in an overshoot condition (step S214). Therefore, a convergence steering torque is calculated as the target steering torque T.

On the other hand, if it is judged as the result of the judgment in step S211 that the ratio of the cornering force F _{r of} the rear wheels 7 and 8th to the steering angle δ of the front wheels 5 and 6 is not greater than the predetermined threshold OS1 (step S211: No), it is judged whether a ratio of the roll angle RA to the turning angle δ of the front wheels 5 and 6 is greater than a predetermined threshold OS2 or not (step S212).

If judged as the result of the judgment in step S212 that the ratio of the roll angle RA to the turning angle δ of the front wheels 5 and 6 is greater than the predetermined threshold OS2 (step S212: Yes), it is judged that the steering is in an overshoot condition (step S214). Therefore, a convergence steering torque is calculated as the target steering torque T.

On the other hand, if it is judged as the result of the judgment in step S212 that the ratio of the roll angle RA to the turning angle δ of the front wheels 5 and 6 is not greater than the predetermined threshold OS2 (step S212: No), it is judged that the steering is not in an overshoot state (ie, the steering is stable) (step S213). Therefore, the basic steering torque is calculated as the target steering torque T.

Incidentally, in addition or instead of the judgment in step S211, it may be judged whether a ratio (ie, F _r / F _f ) of the cornering force F _{r of} the rear wheels 7 and 8th to the cornering force F _{f of} the front wheels 5 and 6 is greater than a predetermined threshold OS3 or not. If it is judged that the ratio of the cornering force F _{r of} the rear wheels 7 and 8th to the cornering force F _{f of} the front wheels 5 and 6 is greater than the predetermined threshold OS3, it is judged that the steering is in an overshoot condition. If judged, the ratio of the cornering force F _{r of} the rear wheels 7 and 8th to the cornering force F _{f of} the front wheels 5 and 6 is not greater than the predetermined threshold OS3, the judgment is made in step S212.

In addition, each of the threshold values OS1, OS2 and OS3 is preferably for each with the electric power steering apparatus 10 provided vehicle 1 experimentally, empirically, mathematically, theoretically or by using simulations or the like in consideration of various features of the vehicle 1 or the like, based on a hysteresis loop between the steering angle δ of the front wheels 5 and 6 and the cornering force F _{r of} the rear wheels 7 and 8th , a hysteresis loop between the steering angle δ of the front wheels 5 and 6 and the roll angle RA, and a hysteresis loop of the cornering force F _{r of} the rear wheels 7 and 8th to the cornering force F _{f of} the front wheels 5 and 6 (Specifically, a hysteresis loop in the case that the vehicle speed is comparatively low and a hysteresis loop in the case that the vehicle speed is comparatively high) are set to a preferable value. However, the setting method is not limited as long as it is preferable to judge whether or not the steering is in an overshooting condition by using the threshold value.

5 FIG. 15 is a flow chart showing the operation of judgment of reverse assistance in step S220 in FIG 3 in conceptual form shows. As shown in 5 In order to judge whether the reverse assistance is being performed or not, it is first judged whether the steering direction of the steering wheel 11 by the driver of a direction in which the by the electric motor 15 applied steering force the front wheels 5 and 6 steers, is opposite or not (step S212).

If judged as the result of the judgment in step S221 that the steering direction of the steering wheel 11 by the driver of the direction in which the by the electric motor 15 applied steering force the front wheels 5 and 6 steers, is opposite (step S212: Yes), it is judged whether the ratio of the cornering force F _{r of} the rear wheels 7 and 8th to the steering angle δ of the front wheels 5 and 6 is greater than a predetermined threshold OS4 or not (step S225). In particular, it is judged whether the steering vibration occurs or not. Therefore, the threshold OS4 is greater than the threshold OS1. In addition, the threshold OS4 will also apply to each with the electric power steering device 10 provided vehicle 1 preferably experimentally, empirically, mathematically, theoretically, or by using simulations or the like in consideration of various features of the vehicle 1 or the like, based on the hysteresis loop between the turning angle δ of the front wheels 5 and 6 and the cornering force F _{r of} the rear wheels 7 and 8th set to a preferred value. However, the setting method is not limited to this as long as it can be judged favorably whether the steering vibration occurs or not.

If judged as the result of the judgment in step S225 that the ratio of the cornering force F _{r of} the rear wheels 7 and 8th to the steering angle δ of the front wheels 5 and 6 is greater than the predetermined threshold OS4 (step S225: Yes), it is judged that the reverse assistance is not present (step S226). Therefore, the convergent steering torque is calculated as the target steering torque T.

On the other hand, if it is judged as the result of the judgment in step S225 that the ratio of the cornering force F _{r of} the rear wheels 7 and 8th to the steering angle δ of the front wheels 5 and 6 is not greater than the predetermined threshold OS4 (step S225: No), it is judged that the reverse assistance is present (step S227). Therefore, the basic steering torque is calculated as the target steering torque T.

On the other hand, if it is judged as the result of the judgment in step S221 that the steering direction of the steering wheel 11 by the driver to the direction in which the by the electric motor 15 applied steering force the front wheels 5 and 6 is steering, not opposite (step S221: No), it is judged whether an absolute value of the steering angle θ of the steering wheel 11 is smaller than a predetermined value OS5_1 or not, and it is judged whether an absolute value of a steering speed (ie, a steering angular velocity dθ) of the steering wheel 11 is smaller than a predetermined value OS5_2 or not (step S222).

If, as a result of the judgment in step S222, it is judged that the absolute value of the steering angle θ of the steering wheel 11 is smaller than the predetermined value OS5_1, and it is judged that the absolute value of the steering speed dθ of the steering wheel 11 is smaller than the predetermined value OS5_2 (step S222: Yes), it is judged that the reverse assistance is present (step S227). Therefore, the basic steering torque is calculated as the target steering torque T.

Incidentally, it can be judged that the inverse assist exists if the absolute value of the steering speed dθ of the steering wheel 11 is smaller than the predetermined value OS5_2, even if the absolute value of the steering angle θ of the steering wheel 11 not smaller than the predetermined value OS5_ 1 is. Moreover, it can be judged that the inverse assist exists if the absolute value of the steering angle θ of the steering wheel 11 is smaller than the predetermined value OS5_1, even if the absolute value of the steering speed dθ of the steering wheel 11 is not smaller than the predetermined value OS5_2.

If, on the other hand, it is judged as the result of the judgment in step S222 that the absolute value of the steering angle θ of the steering wheel 11 is not smaller than the predetermined value OS5_1 or that the absolute value of the steering speed dθ of the steering wheel 11 is not smaller than the predetermined value OS5_2 (step S222: No), it is judged whether the absolute value of the steering angle θ of the steering wheel 11 is greater than a predetermined threshold OS6_1 or not, and it is judged whether the absolute value of the steering speed dθ of the steering wheel 11 is greater than a predetermined threshold OS6_2 or not (step S223).

If, as a result of the judgment in step S223, it is judged that the absolute value of the steering angle θ of the steering wheel 11 is greater than a predetermined threshold OS6_1, and it is judged that the absolute value of the steering speed dθ of the steering wheel 11 is greater than a predetermined threshold OS6_2 (step S223: Yes), it is judged that the reverse assistance is present (step S227). Therefore, the basic steering torque is calculated as the target steering torque T.

Incidentally, it can be judged that the inverse assist exists if the absolute value of the steering speed dθ of the steering wheel 11  is greater than the predetermined value OS6_2, even if the absolute value of the steering angle θ of the steering wheel 11  is not larger than the predetermined value OS6_1. Moreover, it can be judged that the inverse assist exists if the absolute value of the steering angle θ of the steering wheel 11  is greater than the predetermined value OS6_1, even if the absolute value of the steering speed dθ  of the steering wheel 11  is not larger than the predetermined value OS6_2.

On the other hand, if it is determined as the result of the judgment in step S223 that the absolute value of the steering angle θ of the steering wheel 11 is not greater than the predetermined value OS6_1 or that the absolute value of the steering speed de of the steering wheel 11 is not greater than the predetermined value OS6_2 (step S223: No), it is judged whether or not the vehicle is getting 1 is in a einrehenden or suddenly oversteering state (or if there is a possibility that the vehicle 1 in the screw-in state) or not (step S224). The judgment is made on the basis of the control signal S1 derived from the screw-in judging circuit 32 is issued, performed.

If judged as the result of the judgment in step S224 that the vehicle 1 is in the turning state (or that there is a possibility that the vehicle 1 in the screw-in state) (step S224: Yes), it is judged that the reverse assistance is present (step S227). Therefore, the basic steering torque is calculated as the target steering torque T.

On the other hand, if judged as the result of the judgment in step S224 that the vehicle 1 not in the turning state (or there is no possibility that the vehicle 1 in the screw-in state) (step S224: No), it is judged that the reverse assistance is not present (step S226). Therefore, the convergent steering torque is calculated as the target steering torque T.

Here is an in 6 12 is a graph showing the processes in step S222 and step S223 as a relationship between the steering angle θ and the steering speed dθ. If in the diagram in 6 is a combination of the steering angle θ and the steering speed dθ in the hatched area, it is judged that the reverse assistance is not present. If a combination of the steering angle θ and the steering speed dθ is out of the hatched area, it is judged that the inverse assist is present.

Incidentally, the thresholds OS5_1. OS5_2, OS6_1 and OS6_2 for each with the electric power steering device 10 provided vehicle 1 preferably experimentally, empirically, mathematically, theoretically, or by using simulations or the like in consideration of various features of the vehicle 1 or the like is set to preferred values.

7 FIG. 15 is a flowchart showing the calculation operation of calculating the basic steering torque in step S230 in FIG 3 in conceptual form shows. As shown in 7 For example, in order to calculate the basic steering torque, first various signals (eg, the vehicle speed V, the steering torque MT or the like) required to calculate the basic steering torque are read in (step S231). Then, the basic steering torque is calculated on the basis of the various signals read in step S231 (step 232).

In particular, the basic steering torque is calculated on the basis of a diagram that has an in 8th shown relationship between the steering torque MT and the base steering torque shows calculated. To get a margin (a game) in the steering wheel 11 ensure the base steering torque is calculated as 0, if the steering torque MT comparatively is low. If the steering torque MT has a certain level, the calculated base steering torque increases with increasing steering torque MT. If the steering torque MT is greater than a predetermined value, the calculated base steering torque does not change depending on the magnitude of the steering torque MT and becomes a fixed value. Then, the value of the base steering torque with increasing vehicle speed V can be reduced.

9 FIG. 15 is a flowchart showing the procedure of calculation of the convergence steering torque in step S240 in FIG 2 in conceptual form shows. As shown in 9 In the calculation of the convergence steering torque, first, vehicle speed dependency coefficients K _V1 and K _{V2 are} set (to step S241).

Specifically, the vehicle speed _{dependency coefficient} K _{V1 is set} on the basis of a map having an in 10 shown relationship between the vehicle speed _{dependency coefficient} K _V1 and the vehicle speed V shows. Similarly, the vehicle speed _{dependency coefficient} K _{V2 is set} on the basis of a graph showing an in 11 shown relationship between the vehicle speed _{dependency coefficient} K _V2 and the vehicle speed V shows.

The vehicle speed _{dependency coefficients} K _V1 and K _V2 , which in 10 and 11 can be shown by equations of motion, which indicate the movement of the vehicle 1 in one level. In particular, the equations of motion of the vehicle 1 expressed by equations 1 to 4, in which the moment of inertia of the vehicle 1 l is a distance between a front wheel axle and the position of the center of gravity of the vehicle 1 L _f is a distance between a rear wheel axle and the position of the center of gravity of the vehicle 1 L _r is a slip amount L _t is a slip angle of the vehicle 1 β is a cornering force of the front wheel side K _f , and a cornering force on the rear wheel side K _r is.

[Equation 1]

• Iγ. = F _f L _f - F _r L _r

[Equation 2]

[Equation 3]

[Equation 4]

In addition, the electric power steering device applies 10 in the embodiment, a moment input method. Therefore, the following Equation 5 applies, in which the moment of inertia of the front wheels 5 and 6 I _h is, the viscosity coefficient C _h and the steering torque T _h .

[Equation 5]

• I _h δ .. + C _h δ. + F _f L _t = T _h

If the target steering torque T using the equations 1 to 5 with a focus on inhibition of the yaw vibration of the vehicle 1 (in other words an increase in the damping of the vehicle 1 ) is obtained (that is, if an equation obtained by substituting the target steering torque T in the right side of Equation 5 is solved), it becomes necessary that the target steering torque T (in this case, the convergence steering torque) is required the basis of the cornering force F _{r of} the rear wheels 7 and 8th and the differential value of the cornering force F _r . Specifically, it turns out that it is necessary to set the target steering torque T to the sum of a value obtained by multiplying the cornering force F _{r of} the rear wheels 7 and 8th with a certain coefficient A, and a value obtained by multiplying the differential value dF _{r of} the cornering force F _{r of} the rear wheels 7 and 8th with a certain coefficient B. The coefficients A and B respectively correspond to the vehicle speed _dependency coefficients K _V1 and K _V2 .

Each of the vehicle _speed dependency _coefficients K _V1 and K _{V2 obtained} in the above manner changes depending on the vehicle speed V, as shown in FIG 10 and 11 is shown.

In particular, a sign of the vehicle speed dependency coefficient K _{V1 is} reversed at a certain vehicle speed (in particular in a neutral steering state). In particular, the vehicle _speed dependency _coefficient K _{V1 has} a positive value below the determined vehicle speed and has the Vehicle speed _{dependency coefficient} K _{V1 has} a negative value above the determined vehicle speed. This indicates that the target steering torque T is set in consideration of the steering in a direction opposite to the steering direction of the driver (in other words, making it harder for the driver to turn the steering wheel) to inhibit oversteer (ie, to inhibit the yaw vibration of the vehicle) because the vehicle is slightly oversteer above the determined speed. That is, it indicates that the target steering torque T is set to the behavior of the vehicle 1 to stabilize.

As described above, the convergent steering torque can be calculated as the target steering torque T on the basis of an equation of K _V1 × F _r + K _V2 × dF _r. In contrast, however, depending on the behavior of the vehicle 1 or the like application of the aforementioned convergence steering torque unaltered the behavior of the vehicle 1 deteriorate. Therefore, in the embodiment, the convergence steering torque is calculated by further executing the following operation.

In particular, first in 9 a rough road coefficient K _{B is} set (step S242). The rough road coefficient K _B is set to a numerical value in a range between 0 and 1. If the vehicle 1 On a bad road (eg, a road on which the vehicle speed V irregularly or unexpectedly changes significantly, such as a road having a low μ and a rough road), the rough road coefficient K _{B is set} to 0. Alternatively, the rough road coefficient K _{B may be set} to a value greater than 0 and less than 1 when the vehicle 1 driving on a bad road. In contrast, if the vehicle 1 does not drive on a bad road (ie if the vehicle 1 on a normal road such as a paved road), the rough road coefficient K _{B is set} to 1.

Then, the longitudinal acceleration coefficient K _{A is} set (step S243). The longitudinal acceleration coefficient K _A is set to a numerical value in a range between 0 and 1.

In particular, the longitudinal acceleration coefficient K _{A is determined} in accordance with a in 12 set diagram shown. 12 FIG. 12 is a graph showing the value of the longitudinal acceleration coefficient K _A with respect to the absolute value of the longitudinal acceleration α. As it is in 12 is shown, the longitudinal acceleration coefficient K _{A is set} to 1 when the absolute value of the longitudinal acceleration α of the vehicle 1 is equal to or less than a predetermined value. If the absolute value of the longitudinal acceleration α of the vehicle 1 is equal to or greater than the predetermined value, the longitudinal acceleration coefficient K _A with increasing absolute value of the longitudinal acceleration α of the vehicle 1 set smaller. Alternatively, the longitudinal acceleration coefficient K _{A may be set} to 0 if the absolute value of the longitudinal acceleration α of the vehicle 1 is equal to or greater than a predetermined value or if pitching motion in the vehicle 1 occurs.

As well as in 13 2, the longitudinal acceleration coefficient K _{A may be set} in accordance with an elapsed time from the beginning of changing the longitudinal acceleration α an. 13 FIG. 15 is a graph showing the value of the longitudinal acceleration coefficient K _A with respect to an elapsed time from the beginning of changing the longitudinal acceleration α. If the longitudinal acceleration α begins to change, as in 13 shown the longitudinal acceleration coefficient K _A to be set to 0, until a time, the one for the vehicle 1 typical nick cycle corresponding time is elapsed. The longitudinal acceleration coefficient K _A may be set to gradually become large with time after the time corresponding to the pitch cycle has elapsed.

Again in 9 Then, the ABS coefficients K _x1 and K _{x2 are} set (step S244). The ABS coefficients K _x1 and K _x2 are set to a numerical value in a range between 0 and 1.

In particular, the ABS coefficients K _x1 and K _{x2 are determined} in accordance with an in 14 set diagram shown. 14 _{Figure 11} is a graph showing the values of the ABS coefficients K _x1 and K _x2 over time. As it is in 14 is shown, each of the ABS coefficients K _x1 and K _{x2 is set} to 0 if the ABS control is performed. Whether the ABS control is performed or not can be judged from the control signal S2 derived from the ABS control circuit 33 is issued. Hereinafter, if the ABS control is terminated, first, the ABS coefficient K _x2 is set to gradually become larger as time passes. After lapse of a predetermined time since the ABS control is finished, the ABS coefficient K _x1 is set so as to gradually become larger as the time passes. In this case, an increment per unit time of the ABS coefficient K _{x2 is} greater than an increment per unit time of the ABS coefficient K _x1 . In other words, the slope of the curve of the ABS coefficient K _x1 is gentler than the slope of the curve of the ABS coefficient K _x2 , as in 14 is shown.

Incidentally, instead of the process of gradually increasing the ABS coefficient K _x1 and the ABS coefficient K _x2 after completion of the ABS control, the ABS coefficient K _{x2 may be set} to 1 in a certain period after completion of the ABS control, and of the ABS coefficient K _{x1 can be set} to 0, and then the ABS coefficient K _x1 can be set to 1 after further lapse of a predetermined period of time.

Moreover, even in the case where the longitudinal force control such as VSC and TRC is performed, the ABS coefficients K _x1 and K _{x2 are} preferably set in the same respects as those in the ABS control.

Again in 9 Then, a suspension (or SUS) coefficient K _{Z is} set (step S245). The SUS coefficient K _Z is set to a numerical value in a range between 0 and 1. Specifically, the SUS coefficient K _{Z is set} to 1 if the suspension control is not performed. Whether or not the suspension control is performed may be determined from the control signal S3 derived from the SUS control circuit 34 will be judged. On the other hand, if the suspension control is performed, the SUS coefficient K _{Z is set} to 0 or a value greater than 0 and less than 1.

Moreover, even in the case where vertical load control such as stabilizer control is performed, the SUS coefficient K _{Z is} preferably set in the same manner as in the suspension control.

Incidentally, when the vehicle speed V has an abnormality (for example, if the phenomenon of aquaplaning or the like occurs), the vehicle speed _dependency coefficient K _{V1 is} preferably set to 0.

Thereafter, a coefficient K ₁ , with which the cornering force F _{r of} the rear wheels 7 and 8th is actually multiplied calculated (step S246). In particular, K = K ₁ applies _V1 × K _B + K _A × K × K _{Z X1.} In the same way, a coefficient K ₂ , with which the differential value dF _{r of} the cornering force F _{r of} the rear wheels 7 and 8th is actually multiplied calculated (step S247). In particular, K ₂ = K _V2 × K _X2 . After this, the cornering force F _{r of} the rear wheels 7 and 8th and the differential value dF _{r of} the cornering force F _{r of} the rear wheels 7 and 8th calculated (step S248). After that, the convergence steering torque is calculated on the basis of the K ₁ calculated in step S246, the K ₂ calculated in step S247, and the dF _r and F _r calculated in step S248 (step S249).

This is when the steering direction of the steering wheel 11 by the driver is a striking or steering direction, the steering assist force according to the calculated convergence steering torque from the electric motor 15 preferably applied such that the front wheels 5 and 6 in the direction of neutral, as compared with the case where it is judged that the steering is not in an overshooting condition (ie, the judgment that the judgment is made in step S210 in FIG 3 No). If, in contrast, the steering direction of the steering wheel 11 by the driver is a returning or returning direction, the steering assist force becomes in accordance with the calculated convergence steering torque from the electric motor 15 preferably applied such that the front wheels 5 and 6 in an end direction as compared with the case where it is judged that the steering is not in an overshooting condition.

As explained above, according to the embodiment, it is possible to preferably judge whether or not the steering is in an overshooting condition. Then, if the steering is in an overshoot condition, the convergence steering torque may be set as the target steering torque T. Therefore, even when the steering is in an overshooting state, the vibration of the steering and the yaw vibration of the vehicle can be prevented from being coupled with each other (in particular, resonating in a reverse phase with each other). This can cause a convergence of the vibration of the front wheels 5 and 6 cause. That is, it is possible the convergence behavior of the vehicle 1 Improve the convergence behavior of the steering system.

After the convergence steering torque based on the equations of motion in the plane of the vehicle 1 In addition, given the contribution from the torque input, it is possible to calculate the convergence steering torque with high accuracy (or more optimally).

In addition, it is by observing the turning angle δ of the front wheels 5 and 6 , the cornering force F _{f of} the front wheels 5 and 6 , the cornering force F _{r of} the rear wheels 7 and 8th , the roll angle RA or the like, it is possible to judge, preferably or with high accuracy, whether or not the steering is in an overshoot condition.

In particular, it is after the ratio of the roll angle RA to the turning angle δ of the front wheels 5 and 6 is monitored, as in step S212 in 4 is shown, it is possible, preferably or with high accuracy to judge whether the steering is in an overshooting condition, even if the vehicle 1 a high vehicle height such as a minivan and SUV (Sport Utiliy Vehicle or SUV) has. Considering such a merit, a structure may be provided such that the process in step S212 in FIG 4 selectively perform on a vehicle with a high vehicle height and the process in step S212 in 4 to perform on a vehicle with a low vehicle height such as a sports car-type sedan and a coupe.

Moreover, taking into account that it is very likely that the driver performs emergency steering or evasive maneuver, if the steering direction by the driver of the direction in which the steering force caused by the electric motor 15 is applied, the front wheels 5 and 6 is opposite, as in step S221 in 5 is shown, it is possible to prevent a deterioration of the avoidance maneuver by setting the base steering force in accordance with the driver's steering as the target steering torque T. That is, it is possible to respect the driver's desire for emergency steering.

However, it is also when the steering direction by the driver of the direction in which the by the electric motor 15 applied steering force the front wheels 5 and 6 By contrast, by setting the convergence steering torque as the target steering torque T possible, the stability of the vehicle is controlled 1 to emphasize more than the steering feel when the steering vibration occurs or possibly occurs, as in step S225 in FIG 5 is shown.

Incidentally, it is when the steering direction by the driver of the direction in which by the electric motor 15 applied steering force the front wheels 5 and 6 deflects, is opposite, also possible, the coefficient K ₁ , with which the cornering force F _{r of} the rear wheels 7 and 8th actually multiplied, which is the basis for setting the steering force in the direction opposite to the steering direction by the driver. In addition, it is possible to have a contribution ratio of a proportional value of the cornering force F _{r of} the rear wheels 7 and 8th to decrease when the convergence steering torque is calculated.

Moreover, considering that the driver is comparatively small in the range that the absolute value of the steering angle θ and the absolute value of the steering speed dθ, a change in the steering feeling easily feels as it is in step S222 in FIG 5 1, the basic steering torque according to the steering torque MT is set as the target steering torque T, thereby preventing the driver's steering feeling from deteriorating.

Moreover, in consideration of that in the range that the absolute value of the steering angle θ and the absolute value of the steering speed dθ are comparatively large, it is likely that the driver performs emergency steering as in step S223 in FIG 5 is shown, it is possible to respect the will of the driver with respect to emergency steering by setting the basic steering torque according to the steering torque MT as the target steering torque T.

Moreover, it is when the screwing occurs, taking into account that the cornering force F _{r of} the rear wheels 7 and 8th due to the screwing slightly changes or the desired cornering force F _r by the steering of the front wheels 5 and 6 because of the screwing-in is not necessarily obtained, as in step S224 in 5 is shown possible to set the base steering torque according to the steering torque MT as the target steering torque T.

In addition, if the vehicle 1 Driving on the bad road, as in step S242 in 9 is shown, the convergence steering torque can be desirably calculated by eliminating as much as possible the influence of a bad road by making the contribution ratio of the differential value dF _{r of} the Lateral force F _r of the rear wheels 7 and 8th , which includes strong noise in the calculation of the convergence steering torque, or by setting the contribution ratio to 0 (in other words, by the convergence steering torque based on the cornering force F _{r of} the rear wheels 7 and 8th , which includes a low noise, is calculated).

In addition, if the vehicle 1 accelerated or decelerated as indicated in step S243 in FIG 9 5, the convergence steering torque is desirably calculated with the greatest possible elimination of an influence by the acceleration or deceleration, by the contribution ratio of the cornering force F _{r of} the rear wheels 7 and 8th that significantly changes due to the acceleration or the deceleration, is reduced in the calculation of the convergence steering torque, or by setting the contribution ratio to 0 (in other words, by the convergence steering torque based on the differential value dF _{r of} the cornering force F _{r of} the rear wheels 7 and 8th which is not so significantly changed by the acceleration and deceleration).

In addition, when the longitudinal force control such as the ABS control on the vehicle 1 is performed as shown in step S244 in 9 is shown, the convergence steering torque is calculated with the greatest possible elimination of an influence by the longitudinal force control desirably, by the contribution ratio of the cornering force F _{r of} the rear wheels 7 and 8th which significantly changes due to the longitudinal force control, is reduced in the calculation of the convergence steering torque, or by setting the contribution ratio to 0 (in other words, the convergence steering torque based on the differential value dF _{r of} the cornering force F _{r of} the rear wheels 7 and 8th , which does not change so significantly due to the longitudinal force control, is calculated.)

Moreover, when the vertical load control such as the suspension control is performed as in step S245 in FIG 9 is shown, the convergence steering torque can be desirably calculated by eliminating an influence by the vertical load control as much as possible by adjusting the contribution ratio of the cornering force F _{r of} the rear wheels 7 and 8th that significantly changes due to the vertical load control, is reduced in the calculation of the convergence steering torque, or by setting the contribution ratio to 0 (in other words, by the convergence steering torque based on the differential value dF _{r of} the cornering force F _{r of} the rear wheels 7 and 8th which is not so significantly changed due to the vertical load control).

Moreover, when the vehicle speed V has an abnormality, the convergence steering torque with as much as possible elimination of an influence by the abnormality of the vehicle speed V can be desirably calculated by the contribution ratio of the significantly changing cornering force F _{r of} the rear wheels 7 and 8th with respect to the calculation of the convergence steering torque or by setting the contribution ratio to 0 (in other words, by the convergence steering torque based on the differential value dF _{r of} the cornering force F _{r of} the rear wheels 7 and 8th that does not change so significantly).

Incidentally, in the aforementioned embodiment, the front wheels become 5 and 6 on the basis of the steering torque MT and the target steering torque T steered. However, it is also in a so-called active steering, in which the steering of the front wheels 5 and 6 is performed by an actuator based on the steering angle θ, it is possible to obtain the above-mentioned various advantages by executing the steering in the same manner as that of the aforementioned operation in the case where the steering is in an overshooting condition.

(3) Modified Examples

Next, referring to 15 and 16 an explanation regarding modified examples of the electric power steering apparatus 10 in the embodiment.

(3-1) First modified example

15 Fig. 10 is an outline structural view conceptually showing the basic structure of a first modified example of the embodiment of the vehicle steering control apparatus of the present invention. As shown in 15 is in addition to the electric power steering apparatus in the first modified example 10 for steering the front wheels 5 and 6 Further, an electric power steering apparatus 50 for steering the rear wheels 7 and 8th intended.

The electric power steering device 50 For example, a rack-type electric power steering apparatus is provided with: an electric motor 55 for generating an auxiliary steering force for steering the rear wheels 7 and 8th and for applying the auxiliary steering force to a steering shaft 52 by means of a reduction gear, not shown; and a rack and pinion mechanism 56 ,

In the first modified example having such a structure, the rear wheels become 7 and 8th steered, if the steering direction of the steering wheel 11 by the driver is opposite to the direction in which the by the electric motor 15 applied steering force the front wheels 5 and 6 directs. At this time, the above-mentioned basic steering torque becomes the target steering torque T from the ECU 30 to the electric motor 15 for steering the front wheels 5 and 6 output.

By steering the rear wheels 7 and 8th It is possible the yaw moment on the other side of the vehicle 1 to change. That is, in the embodiment described with reference to 1 to 14 has been explained, the yaw moment of the steering by setting the convergence steering torque T as the target steering torque T of the electric motor 15 changed. In the first modified example, on the other hand, the yaw moment becomes on the other side of the vehicle 1 changed. Even if the yaw moment on the other side of the vehicle 1 is changed in this way, it is possible to prevent the vibration of the steering and the yaw vibration of the vehicle are coupled to each other (in particular, due to the fact that they resonate each other in the reverse phase), as described above. This can cause a convergence of the vibration of the front wheels 5 and 6 cause. That is, it is possible the convergence behavior of the vehicle 1 Improve the convergence behavior of the steering system.

In addition, there is such an advantage that the driver's steering feeling does not deteriorate since the front wheels 5 and 6 setting the base steering torque according to the steering torque MT as the target steering torque T.

(3-2) Second modified example

16 Fig. 10 is an outline structural view conceptually showing the basic structure of a second modified example of the embodiment of the vehicle steering control apparatus of the present invention. As shown in 16 are in the second modified example, an active steering actuator 61 for steering the front wheel 5 and an active steering wheel 62 for steering the front wheel 6 intended. The active steering wheel 61 and 62 steer the front wheels 5 and 6 on the basis of a target turning angle δ _L and a target turning angle δ _{R of} the front wheel 6 coming from the ecu 30 are output, each such that the steering angle of the front wheel 5 δ _L becomes and the turning angle of the front wheel 6 δ _R becomes.

In the second modified example, as described above, the target turning angles δ _L and δ _{R are set} such that the front wheels 5 and 6 a toe if it is judged that the steering is in a Überschnugungszustand.

As described above, by adjusting the front wheels 5 and 6 in that they have a toe, a cornering capacity C _{p of} the front wheels 5 and 6 to thereby change the natural frequency value of the front wheels 5 and 6 to change. By doing so, the vibration of the steering and the yaw vibration of the vehicle can be prevented from being coupled with each other (in particular, they resonate with each other in the reverse phase) as described above. This can cause a convergence of the vibration of the front wheels 5 and 6 cause. That is, it is possible the convergence of the vehicle 1 improve the convergence of steering.

The present invention is not limited to the above-mentioned embodiment, and various changes can be made without departing from the spirit or idea of the invention which can be seen from the claims and the entire description. A vehicle steering control apparatus incorporating such changes is also intended to be within the technical scope of the present invention.

Claims (27)

Vehicle steering control device ( 30 ), which comprises: a steering force application device ( 10 . 15 ) for applying a steering force at least on front wheels ( 5 . 6 ); and characterized by a lateral guide force detection device ( 42 ) for detecting a cornering force (F _f , F _r ) of both the front wheels ( 5 . 6 ) as well as the rear wheels ( 7 . 8th ), wherein the steering force application device ( 10 . 15 ) on the front wheels ( 5 . 6 ) applies a first steering force which the front wheels ( 5 . 6 ) in a direction in which a yaw vibration converges, if a ratio of the cornering force (F _r ) of the rear wheels (F _r ) of the rear wheels ( 7 . 8th ) to the cornering force (F _f ) of the front wheels ( 5 . 6 ) becomes a ratio that possibly the yaw vibration in the vehicle ( 1 ) caused. Vehicle steering control device ( 30 ) according to claim 1, characterized in that the steering force application device ( 10 . 15 ) (i) as the first steering force exerts a steering force which the front wheels ( 5 . 6 ) in the direction of the neutral position, if the steering by a driver of the vehicle ( 1 ) is in a striking or steering state, and (ii) as the first steering force exerts a steering force that the front wheels ( 5 . 6 ) in a direction of impact, if the steering by the driver of the vehicle ( 1 ) is in a returning or returning state. Vehicle steering control device ( 30 ) according to claim 1, characterized in that the steering force application device ( 10 . 15 ) applies the steering force to a steering angle (δ) of the front wheels ( 5 . 6 ) to control. Vehicle steering control device ( 30 ) according to claim 1, characterized in that the steering force application device ( 10 . 15 ) on the front wheels ( 5 . 6 ) applied steering force based on a steering torque (MT) according to the steering operation of a driver of the vehicle ( 1 ) controls. Vehicle steering control device ( 30 ) according to claim 1, characterized in that the steering force application device ( 10 . 15 ) applies the first steering force if the ratio of the cornering force (F _r ) of the rear wheels ( 7 . 8th ) to the cornering force (F _f ) of the front wheels ( 5 . 6 ) is greater than a first predetermined threshold (OS3). Vehicle steering control device ( 30 ) according to claim 1, characterized in that the steering force application device ( 10 . 15 ) applies the first steering force if a first value obtained by dividing the cornering force (F _r ) of the rear wheels ( 7 . 8th ) is obtained by a steering angle (δ) of the front wheels is greater than a second predetermined threshold (OS1, OS4). Vehicle steering control device ( 30 ) according to claim 1, characterized in that the steering force application device ( 10 . 15 ) applies the first steering force, if a second value, the one by the division of a roll angle (Ra) of the vehicle ( 1 ) by a steering angle (δ) of the front wheels ( 5 . 6 ) is greater than a third predetermined threshold (OS2). Vehicle steering control device ( 30 ) according to claim 1, characterized in that the steering force application device ( 10 . 15 ) the first steering force based on both a third value that is a value proportional to the cornering force (F _r ) of the rear wheels ( 7 . 8th ), as well as a fourth value (dF _r ) obtained by deriving the cornering force of the rear wheels ( 7 . 8th ) is obtained after the time. Vehicle steering control device ( 30 ) according to claim 1, characterized in that the steering force application device ( 10 . 15 ) the first steering force according to a speed (V) of the vehicle ( 1 ) corrected. Vehicle steering control device ( 30 ) according to claim 9, characterized in that the steering force application device ( 10 . 15 ) reduces the first steering effort when the vehicle ( 1 ) drives on a bad road. Vehicle steering control device ( 30 ) according to claim 10, characterized in that the steering force application device ( 10 . 15 ) the first steering force based on both a third value (F _r ) having a value proportional to the cornering force (F _r ) of the rear wheels ( 7 . 8th ), as well as a fourth value (dF _r ) which is a value obtained by deriving the cornering force (F _r ) of the rear wheels ( 7 . 8th ) is obtained after the time so that a contribution ratio (K ₂ ) of the fourth value (dF _r ) used when the vehicle ( 1 ) is on the bad road, is smaller than a contribution ratio (K ₂ ) of the fourth value (dF _r ) used when the vehicle ( 1 ) on a normal road. Vehicle steering control device ( 30 ) according to claim 1, characterized in that the steering force application device ( 10 . 15 ) the first steering force based on a movement model of the vehicle ( 1 ) in one plane. Vehicle steering control device ( 30 ) according to claim 12, characterized in that the steering force application device ( 10 . 15 ) the first steering force based on the motion model of the vehicle ( 1 ) is calculated in the plane in which an input by a steering torque (T) shows. Vehicle steering control device ( 30 ) according to claim 1, characterized in that the steering force application device ( 10 . 15 ) reduces the first steering force if an absolute value of a steering angle (θ) and / or an absolute value of a steering speed (dθ) is equal to or smaller than a predetermined fourth threshold (OS5_1, OS5_2). Vehicle steering control device ( 30 ) according to claim 1, characterized in that the steering force application device ( 10 . 15 ) reduces the first steering force if an absolute value of a steering angle (θ) and / or an absolute value of a steering speed (dθ) is equal to or greater than a predetermined fifth threshold (OS6_1, OS6_2). Vehicle steering control device ( 30 ) according to claim 1, characterized in that the steering force application device ( 10 . 15 ) reduces the first steering force if a steering direction by a driver of the vehicle ( 1 ) is opposite to a direction in which the steering force is applied. Vehicle steering control device ( 30 ) according to claim 1, characterized in that the steering force application device ( 10 . 15 ) the steering force on the rear wheels ( 7 . 8th ) applies if a steering direction by a driver of the vehicle ( 1 ) is opposite to a direction in which the steering force is applied. Vehicle steering control device ( 30 ) according to claim 16, characterized in that when a steering vibration occurs, the steering force application device ( 10 . 15 ) applies the first steering force even when the steering direction by the driver of the vehicle ( 1 ) is opposite to the direction in which the steering force is applied. Vehicle steering control device ( 30 ) according to claim 1, characterized in that the steering force application device ( 10 . 15 ) reduces the first steering force, if a longitudinal force control which a longitudinal force of the vehicle ( 1 ) on the vehicle ( 1 ) is carried out. Vehicle steering control device ( 30 ) according to claim 19, characterized in that the steering force application device ( 10 . 15 ) the first steering force based on both a third value (F _r ) that is a value proportional to the cornering force of the rear wheels ( 7 . 8th ) is calculated as well as a fourth value (dF _r ) which is obtained by the cornering force (F _r ) of the rear wheels ( 7 . 8th ) is derived after the time, if the longitudinal force control on the vehicle ( 1 ) is not performed, and the steering force application device ( 10 . 15 ) the first steering force is calculated on the basis of the third value (F _r ) and the fourth value (dF _r ) so that a contribution ratio (K ₁ ) of the third value (F _r ) used when the longitudinal force control is performed is smaller than a contribution ratio (K ₁ ) of the third value (F _r ) used if the longitudinal force control is not performed. Vehicle steering control device ( 30 ) according to claim 20, characterized in that the steering force application device ( 10 . 15 ) does not apply the first steering force if the longitudinal force control which changes the longitudinal force of the vehicle ( 1 ), and the steering force application device (FIG. 10 . 15 ) first applies the first steering force calculated on the basis of the fourth value (dF _r ) during a predetermined period after completion of the longitudinal force control and then applies the first steering force obtained by gradually increasing the contribution ratio of the third value (F _r ) in FIG Is calculated over time. Vehicle steering control device ( 30 ) according to claim 1, characterized in that the steering force application device ( 10 . 15 ) calculates the first steering force on the basis of both a third value proportional to the cornering force (F _r ) of the rear wheels and a fourth value (dF _r ) obtained by deriving the cornering force (F _r ) of the rear wheels ( 7 . 8th ), wherein a contribution ratio (K ₁ ) of the third value (F _r ) is reduced the more, the more an acceleration or deceleration of the vehicle ( 1 ) increases. Vehicle steering control device ( 30 ) according to claim 1, characterized in that the steering force application device ( 10 . 15 ) the first steering force based on both a third value (F _r ) having a value proportional to the cornering force (F _r ) of the rear wheels ( 7 . 8th ) as well as a fourth value (dF _r ) obtained by deriving the cornering force (F _r ) of the rear wheels ( 7 . 8th ) after the time is calculated such that a contribution ratio (K ₁ ) of the third value (F _r ) determined in a predetermined period of time after the change of the acceleration or deceleration of the vehicle ( 1 ) is less than a contribution ratio (K ₁ ) of the third value (F _r ) used when acceleration and deceleration of the vehicle ( 1 ) are constant. Vehicle steering control device ( 30 ) according to claim 1, characterized in that the steering force application device ( 10 . 15 ) reduces the first steering force, if a load control is performed, which is a vertical load of the front wheels ( 5 . 6 ) changes. Vehicle steering control device ( 30 ) according to claim 1, characterized in that the steering force application device ( 10 . 15 ) reduces the first steering force if there is a possibility that a predetermined behavior of the vehicle ( 1 ) occurs in the reduction of vehicle power during cornering, or if the predetermined behavior of the vehicle ( 1 ) occurs. Vehicle steering control device ( 30 ) according to claim 1, characterized in that the steering force application device ( 10 . 15 ) a natural frequency value changing device ( 61 . 62 ) for changing a natural frequency value of the front wheels ( 5 . 6 ) in a case that there is a possibility that the cornering force (F _r ) of the rear wheels (F _r ) of the rear wheels (F _r ) 7 . 8th ) the front wheels ( 5 . 6 ) vibrated. Vehicle steering control device ( 30 ) according to claim 26, characterized in that the natural frequency value changing device ( 61 . 62 ) is capable of both the front wheel ( 6 ), which is located on a right side, as well as the front wheel ( 5 ) located on the left side, each having different turning angles (δ _R , δ _L ), and the natural frequency value changing device (FIG. 61 . 62 ) a steering force for steering the front wheels ( 5 . 6 ) in the toggle direction, if there is a possibility that the cornering force (F _r ) of the rear wheels (F _r ) of the rear wheels ( 7 . 8th ) the front wheels ( 5 . 6 ) vibrated.

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